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United States Patent |
5,158,276
|
Toma
|
October 27, 1992
|
Sheet feeding apparatus
Abstract
The invention relates to a sheet feeding apparatus comprising a first
mounting position for mounting a first accommodating device accommodating
sheets therein, a second mounting position for mounting a second
accommodating device accommodating sheets therein, a first sheet feeding
device for feeding the sheet from the first accommodating device mounted
to the first mounting position, a second sheet feeding device for feeding
the sheet from the second accommodating device mounted to the second
mounting position, and a support means for supporting the first
accommodating device or for supporting a third accommodating device
accommodating sheets therein and having such a size as to occupy the first
and second mounting positions in a position where the sheet can be fed by
the first sheet feeding device from the first or third accommodating
device.
Inventors:
|
Toma; Akihiro (Tokyo, JP)
|
Assignee:
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Canon Kabushiki Kaisha (Tokyo, JP)
|
Appl. No.:
|
740875 |
Filed:
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July 31, 1991 |
Foreign Application Priority Data
| Apr 20, 1988[JP] | 63-097147 |
Current U.S. Class: |
271/9.11; 271/164 |
Intern'l Class: |
B65H 003/44 |
Field of Search: |
271/9,162,164
|
References Cited
U.S. Patent Documents
4436406 | Mar., 1984 | Murasaki | 271/9.
|
4569586 | Feb., 1986 | Koyama | 271/9.
|
Primary Examiner: Schacher; Richard A.
Attorney, Agent or Firm: Fitzpatrick, Cella, Harper & Scinto
Parent Case Text
This application is a continuation of application Ser. No. 07/340,262 filed
Apr. 19, 1989, now abandoned.
Claims
I claim:
1. A sheet feeding apparatus comprising:
a first mounting station for mounting a first accommodating means
accommodating sheets therein;
a second mounting station for mounting a second accommodating means
accommodating sheets therein;
a first sheet feeding means for feeding the sheet from said first
accommodating means mounted to said first mounting station;
a second sheet feeding means for feeding the sheet from said second
accommodating means mounted to said second mounting station; and
a support means for supporting said first accommodating means or for
supporting a third accommodating means accommodating sheets therein and
having such a size as to occupy said first and second mounting stations in
a sheet feeding position, wherein said first sheet feeding means and said
second sheet feeding means are vertically arranged in an upper and lower
relation without offset in the horizontal direction.
2. A sheet feeding apparatus according to claim 1, further including a
shift preventing means for preventing movement of said first accommodating
means mounted to said first mounting station or movement of said third
accommodating means.
3. A sheet feeding apparatus according to claim 1, wherein said support
means includes an engagement member for engaging by said first or third
accommodating means.
4. A sheet feeding apparatus according to claim 3, wherein said engagement
member supports said first or third accommodating means.
5. A sheet feeding apparatus according to claim 4, wherein said engagement
member supports said first or third accommodating means at both sides
thereof.
6. A sheet feeding apparatus according to claim 1, wherein said third
accommodating means is supported in an inclined condition not to be
abutted against said second sheet feeding means.
7. A sheet feeding apparatus according to claim 1, wherein said support
means supports selectively and removably either of said first or third
accommodating means.
8. A sheet feeding apparatus according to claim 1, further comprising:
a third sheet feeding means for feeding the sheet from said third
accommodating means, and
a third mounting position for mounting a fourth accommodating means
accommodating sheets therein, and wherein said support means can removably
support a fifth accommodating means accommodating sheets therein and
having such a size as to occupy said first, second and third mounting
stations.
9. A sheet feeding apparatus comprising:
a first sheet feeding means for feeding a sheet;
a first support means for supporting a first accommodating means
accommodating sheets or for supporting a second accommodating means
accommodating sheets therein and having a sheet accommodating capacity
larger than that of said first accommodating means in a sheet feeding
position;
wherein the sheet feeding apparatus forms a space when the first
accommodating means is supported by said first support means, and wherein
the second accommodating means occupies said space when supported by said
first support means;
a second support means for supporting a third accommodating means in said
space; and
a second sheet feeding means for feeding the sheet from said third
accommodating means supported by said second support means, wherein said
first sheet feeding means and said second sheet feeding means are arranged
vertically in an upper and lower relation without offset in the horizontal
direction.
10. A sheet feeding apparatus according to claim 9, wherein said second
support means is arranged below said first support means.
11. A sheet feeding apparatus according to claim 9, wherein said first
support means includes an engagement member for engaging by said first or
second accommodating means.
12. A sheet feeding apparatus according to claim 11, wherein said
engagement member supports said first or second accommodating means.
13. A sheet feeding apparatus according to claim 12, wherein said
engagement member supports said first or second accommodating means at
both sides thereof.
14. A sheet feeding apparatus according to claim 9, further including a
shift preventing means for preventing movement of said first or second
accommodating means supported by said first support means.
15. A sheet feeding apparatus according to claim 9, wherein said second
accommodating means is supported in an inclined condition spaced from said
second sheet feeding means.
16. A sheet feeding apparatus comprising:
a first sheet feeding rotary member for feeding a sheet;
a first supporting member capable of engaging a first accommodating means
accommodating sheets or a second accommodating means accommodating sheets
therein and having a sheet accommodating capacity larger than that of said
first accommodating means for supporting said first or second
accommodating means in a sheet feeding position;
wherein the sheet feeding apparatus forms a space when the first
accommodating means is supported by said first support means, and wherein
the second accommodating means occupies said space when supported by said
first support means;
a second support means for supporting a third accommodating means in said
space; and
a second sheet feeding rotary member for feeding the sheet from said third
accommodating means supported by said second support member, wherein said
first sheet feeding means and said second sheet feeding means are arranged
vertically in an upper and lower relation without offset in the horizontal
direction.
17. An image forming apparatus comprising:
a first sheet feeding means for feeding a sheet;
a first support means for supporting a first accommodating means
accommodating sheets or for supporting a second accommodating means
accommodating sheets therein and having a sheet accommodating capacity
larger than that of said first accommodating means in a sheet feeding
position;
wherein the sheet feeding apparatus forms a space when the first
accommodating means is supported by said first support means, and wherein
the second accommodating means occupies said space when supported by said
first support means;
a second support means for supporting a third accommodating means in said
space; and
a second sheet feeding means for feeding the sheet from said third
accommodating means supported by said second support means;
an image forming means for forming an image on the sheet fed by said first
or second sheet feeding means; and
a conveying means for conveying the sheet on which the image is formed by
said image forming means, wherein said first sheet feeding means and said
second sheet feeding means are arranged vertically in an upper and lower
relation without offset in the horizontal direction.
18. A sheet feeding apparatus according to any of claims 1, 9, 16 or 17,
wherein one of said first, second and third accommodating means is
supported in a sloped condition relative to a horizontal direction so that
a side thereof for feeding out the sheet is located than opposite side.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a sheet feeding apparatus, and, more
particularly, it relates to a sheet feeding apparatus of sheet cassette
mounting or loading type, wherein a sheet cassette within which a
plurality of sheets (cut sheets and the like) are stacked is inserted in a
cassette insertion portion formed in a body of the apparatus and the
sheets are fed one by one at a prescribed timing toward a predetermined
sheet processing position by means of feeding means provided in the body
of the apparatus.
2. Related Background Art
Such a sheet feeding apparatus of sheet cassette mounting type has been
widely used with a conventional recording apparatus such as an electronic
copying machine, electrostatic copying machine, laser beam printer, easy
printer and the like, in order to automatically feed the sheets (transfer
sheets, photosensitive sheets, recording sheets, printing sheets and the
like) one by one toward an image forming mechanism of the recording
apparatus by means of feeding means.
With this arrangement, so long as a plurality of cassettes which have the
same size and/or quality of stacked sheets in the same cassette but have a
different size and/or quality from those of the sheets in other cassettes,
are prepared in advance, it is possible to change the kinds of sheet
merely by inserting a cassette including a desired kind of sheets into the
cassette insertion portion formed in the body of the recording apparatus.
Thus, it is very convenient and is easy to handle and store the sheets.
Alternatively, a multi-layer cassette system has also been adopted. In this
case, a plurality of cassette insertion portions are formed in the body of
the recording apparatus, and the cassettes, each including the different
kind of sheets, are inserted into the respective cassette insertion
portions. An operator designates or selects a desired sheet by the use of
selection designation means provided on the recording apparatus so that
the feeding means associated with the cassette including the desired sheet
are selectively actuated. With this arrangement, since the kinds of sheet
to be fed to the recording apparatus can be changed by manipulating
selection buttons of the selection designation means, the operability is
further improved.
Such conventional sheet feeding apparatus of multi-layer (three layers)
cassette mounting type is shown in FIGS. 7A and 7B, where FIG. 7A is a
side sectional view and FIG. 7B is a rear view of the apparatus.
In these Figures, a body 1 of a recording apparatus such as an electronic
copying machine has three (upper, intermediate, lower) cassette insertion
portions 20.sub.1, 20.sub.2 and 20.sub.3 formed therein, into which sheet
cassettes 30a, 30b and 30c can be removably inserted; feeding means
21.sub.1, 21.sub.2, 21.sub.3 arranged in correspondence with the
respective cassette insertion portions; portions; regist rollers (or relay
feed rollers) 23; and sheet paths (sheet guide passages) 22.sub.1,
22.sub.2 and 22.sub.3 extending between the regist rollers 23 and the
corresponding feeding means 21.sub.1, 21.sub.2 and 21.sub.3.
Each of the sheet cassettes 30a, 30b or 30c includes sheets of different
kind (from those in other cassettes) (for, example, A4 size, B4 size, B5
size and the like) stacked therein. When the cassette 30a, 30b or 30c is
inserted into one of the cassette insertion portions 20.sub.1, 20.sub.2 or
20.sub.3 completely, the kinds of the sheets housed in the sheet cassette
inserted into the cassette insertion portions are detected by means of
detection means (not shown), and the detected kinds (of the sheet) are
displayed on a displayer of the selection means arranged on a console
panel (not shown) of the body 1 of the recording apparatus.
Now, when the operator selects or designates a desired kind (of the sheet)
from among a plurality of kinds displayed on the displayer, only one of
the feeding means 21.sub.1, 21.sub.2 or 21.sub.3 corresponding to the
cassette insertion portion 20.sub.1, 20.sub.2 or 20.sub.3 into which the
sheet cassette 30a, 30b or 30c including the designated kind of sheets is
inserted is in a operable condition, and said feeding means is controlled
to be actuated at a predetermined timing. In this way, the sheets (of the
designated kind) are fed one by one from said sheet cassette, and then,
each sheet passes through the corresponding sheet path 22.sub.1, 22.sub.2
or 22.sub.3, the regist rollers 23 and a sheet passage 24, and is fed to
an image transferring position and other sheet processing positions (not
shown) in the body 1 of the recording apparatus.
In the above-mentioned conventional sheet feeding apparatus of multi-layer
cassette mounting type, each of openings of the cassette insertion
portions 20.sub.1, 20.sub.2 or 20.sub.3 is configurated for the purpose of
receiving any cassettes of the same size (to have the same maximum
capacity for accommodating the same numbers of sheets regardless of the
kinds of the sheet). To this end, the openings of the cassette insertion
portions are formed to have the same configuration by partition plates 25
positioned between the cassette insertion portions. However, such
arrangement results in the following drawbacks:
(1) When it is desired that the sheets of one size are to be used in
greater quantities than the sheets of other sizes, the user or operator
must frequently replenish the empty cassette with new sheets of the
specific size or change the empty cassette to a new cassette including the
sheet of the specific size. Therefore, the recording operation is
interrupted frequently each time the sheets are replenished or the
cassettes are changed, during the operation of the recording apparatus
itself. In order to reduce the interruption of the recording operation, a
cassette having a larger capacity may be used for the sheet of the
specific size in question. However, such cassette having the larger
capacity cannot be inserted in any cassette insertion portions 20.sub.1,
20.sub.2 or 20.sub.3 of the recording apparatus, and thus, cannot be used
with such recording apparatus. (2) On the other hand, if cassette
insertion portions corresponding to the cassette having the larger
capacity are formed in the body of the recording apparatus, the opening of
each cassette insertion portion will be large-sized. Consequently, a
plurality of feeding means cannot be provided in the recording apparatus,
with the result that the request presented by the user or operator who
wishes to use a various kinds of sheets cannot be satisfied.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a sheet
feeding apparatus of sheet cassette mounting or loading type wherein
various sheet cassettes having various sizes and various sheet
accommodating capacities can be freely used and mounted thereon. With this
sheet feeding apparatus, the drawbacks as mentioned in the above items (1)
and (2) can be eliminated.
In other words, it is an object of the present invention to provide a sheet
feeding apparatus of sheet cassette mounting type which is simple in
construction and wherein various sheet cassettes having various sheet
accommodating capacities can be freely mounted thereon at the operator's
need.
In order to achieve the above-mentioned object, the present invention
provides a sheet feeding apparatus of sheet cassette mounting type wherein
a plurality of sheet cassettes each accommodating the sheets can be
inserted into a cassette insertion portion formed in a body of the
apparatus and sheets are fed one by one from one of the sheet cassettes,
and further wherein a plurality of feeding means are provided in
association with a single cassette insertion portion, the same number of
the sheet cassettes as the number of the feeding means can be mounted into
the single cassette insertion portion, and a sheet cassette having a
different sheet accommodating capacity can also be mounted in said
cassette insertion portion across the plurality of feeding means.
With this arrangement, by mounting the same number of sheet cassettes (as
the number of the feeding means provided in the single cassette insertion
portion) in the cassette insertion portion, as in the case of the
conventional sheet feeding apparatus of multi-layer cassette mounting
type, it is possible to selectively actuate the feeding means
corresponding to the cassette including a desired kind of sheets by
designating the desired kind of sheets through the selection designation
means so that the desired sheets can be automatically fed one by one from
the cassette successively. That is to say, only when a plurality of sheet
cassettes each having a smaller capacity and including a respective kind
of sheets are previously inserted into the single cassette insertion
portion, it is possible to easily and frequently change the kinds of sheet
to be used, only by manipulating the selection buttons of the selection
designation means.
On the other hand, when all of the sheet cassettes of the smaller
capacities are removed or dismounted from the single cassette insertion
portion and a single sheet cassette having a larger capacity corresponding
to a space in the cassette insertion portion is inserted into the cassette
insertion portion, or when two or more adjacent sheet cassettes of the
smaller capacities are removed from the cassette insertion portion and a
single sheet cassette having an intermediate capacity corresponding to a
space obtained by the removal of these smaller cassettes is inserted into
the cassette insertion portion, the sheets can be automatically fed one by
one successively from the larger or intermediate cassette by means of an
uppermost feeding means among the plurality of feeding means across which
the larger or intermediate cassette is mounted.
That is to say, if it is desired to particularly use the sheets of specific
size or quality in greater quantities than the other sheets, by using the
sheet feeding apparatus in a condition that such larger or intermediate
cassette is inserted into the cassette insertion portion, it is possible
to reduce the frequency in the replenishment of the sheets and/or the
change of the cassettes, and, therefore, the frequency in the interruption
of the recording operation considerably.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a sheet feeding apparatus according to a first embodiment of
the present invention, wherein FIG. 1A is a longitudinal sectional view of
the sheet feeding apparatus before sheet cassettes are mounted or after
the sheet cassettes are dismounted, FIG. 1B is a longitudinal sectional
view in a condition that the sheet cassettes are mounted on the sheet
feeding apparatus, FIG. 1C is a rear view of the apparatus of FIG. 1B,
FIG. 1D is a longitudinal sectional view in a condition that a sheet
cassette having a larger capacity is mounted on the sheet feeding
apparatus, and FIG. 1E is a rear view of the apparatus of FIG. 1D;
FIG. 2 shows a construction of locking means, wherein FIG. 2A is a
sectional view of the locking means in an unlocked condition and FIG. 2B
is a sectional view of the locking means in a locked condition;
FIG. 3 is an explanatory view showing an example that the sheet feeding
apparatus of the first embodiment is applied to an image forming
apparatus;
FIG. 4 shows a sheet feeding apparatus according to a second embodiment of
the present invention, wherein FIG. 4A is a longitudinal sectional view of
the sheet feeding apparatus before sheet cassettes are mounted or after
the sheet cassettes are dismounted, FIG. 4B is a longitudinal sectional
view in a condition that the sheet cassettes are mounted on the sheet
feeding apparatus, FIG. 4C is a rear view of the apparatus of FIG. 4B,
FIG. 4D is a longitudinal sectional view in a condition that a sheet
cassette having an middle or medium capacity is mounted on the sheet
feeding apparatus, FIG. 4E is a rear view of the apparatus of FIG. 4D,
FIG. 4F is a longitudinal sectional view in a condition that a sheet
cassette having a larger capacity is mounted on the sheet feeding
apparatus, and FIG. 4G is a rear view of the apparatus of FIG. 4F;
FIG. 5 shows a sheet feeding apparatus according to a third embodiment of
the present invention, wherein FIG. 5A is a longitudinal sectional view of
the sheet feeding apparatus before sheet cassettes are mounted or after
the sheet cassettes are dismounted, FIG. 5B is a elevational view showing
a cassette insertion portion, FIG. 5C is a longitudinal sectional view in
a condition that the sheet cassette are mounted on the sheet feeding
apparatus, FIG. 5D is a longitudinal sectional view in a condition that a
sheet cassette having an middle capacity is mounted on the sheet feeding
apparatus, and FIG. 5E is a longitudinal sectional view in a condition
that a sheet cassette having a larger capacity is mounted on the sheet
feeding apparatus;
FIG. 6 shows a sheet feeding apparatus according to a fourth embodiment of
the present invention, wherein FIG. 6A is a longitudinal sectional view in
a condition that the sheet cassettes are mounted on the sheet feeding
apparatus, FIG. 6B is a longitudinal sectional view in a condition that a
sheet cassette having a middle capacity is mounted on the sheet feeding
apparatus, and FIG. 6C is a longitudinal sectional view in a condition
that a sheet cassette having a larger capacity is mounted on the sheet
feeding apparatus;
FIG. 7 shows a conventional sheet feeding apparatus, where FIG. 7A is a
longitudinal sectional view in a condition that the sheet cassettes are
mounted on the sheet feeding apparatus, and FIG. 7B is a rear view of the
apparatus of FIG. 7A.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIGS. 1 and 2 show a first embodiment of the present invention.
In this first embodiment, as shown in FIG. 1A, a single cassette insertion
portion 2 having a larger height is formed in a body 1 of the sheet
feeding apparatus, and two (upper and lower) sheet feeding means (feed
rollers) 2.sub.1 and 2.sub.2 are arranged in the inner part of the
cassette insertion portion 2. Guide slots 2a are formed in both side walls
of the cassette insertion portion 2 at a level of the upper sheet feeding
means 2.sub.1. Similarly, guide slots 2b are also formed in both side
walls of the cassette insertion portion 2 at a level of the lower sheet
feeding means 2.sub.2. These guide slots 2a and 2b extend from an inlet of
the cassette insertion portion to the respective sheet feeding means in
substantially horizontal directions, respectively.
Sheet cassettes 3.sub.1 and 3.sub.2 having the same smaller capacities can
be inserted into the cassette insertion portion in an overlapped relation.
Guide ridges (projecting upper edges) 3a which can engage with the guide
slots 2a or 2b formed in the transverse walls of the cassette insertion
portion 2 are formed on upper ends of both transverse or side walls of the
sheet cassettes 2.sub.1 and 2.sub.2, respectively (see FIG. 1C).
One of the sheet cassettes 3.sub.1 or 3.sub.2 is mounted in the cassette
insertion portion 2 by inserting it into the cassette insertion portion
completely while engaging the guide ridge 3a thereof by the upper guide
slots 2a of the cassette insertion portion 2, and the other sheet cassette
3.sub.2 or 3.sub.1 is also mounted in the cassette insertion portion 2 by
inserting it into the cassette insertion portion completely while engaging
the guide ridge 3a thereof by the lower guide slots 2b of the cassette
insertion portion 2. In the way, two sheet cassettes 3.sub.1, 3.sub.2 are
mounted in the cassette insertion portion 2 in the overlapped relation in
an up-and-down direction, as shown in FIGS. 1B and 1C.
When the sheet cassettes 3.sub.1, 3.sub.2 are fully or completely inserted
in the cassette insertion portion 2 in the above-mentioned manner, the
respective cassettes are locked in their mounted positions by means of the
corresponding locking means.
One example of such locking means is shown in FIG. 2. Each locking means
comprises a locking arm 7 pivotally mounted, through a support shaft, on
an upper outer surface of a channel member 4 forming the guide slot 2a or
2b along which the guide ridge 3a of the cassette 3.sub.1 or 3.sub.2 is
guided and normally biased in a clockwise direction by means of a
corresponding spring 6. The channel member 4 is provided with a through
opening 4a through which a downwardly extending projection 7a formed on
the free end of the locking arm 7 can pass. When the cassette is not
mounted in the cassette insertion portion, as shown in FIG. 2A, the
locking arm 7 has been rotated in a clockwise direction by the pulling
action of the spring 6 until a stopper shoulder 7b of the locking arm is
abutted against the upper outer surface of the channel member 4, where a
tip or free end of the downwardly extending projection 7a of the locking
arm passed through the through opening 4a of the channel member penetrates
into the guide slot 2 a or 2b.
When the cassette 3.sub.1 or 3.sub.2 is inserted into the cassette
insertion portion 2 while engaging the guide ridge 3a thereof by the
corresponding guide slot 2a or 2b, at a point before the cassette is
completely inserted into the cassette insertion portion, an inclined cam
surface 3b formed on an upper edge of a leading end of the guide ridge 3a
of the cassette abuts against the free end of the projection 7a of the
locking arm 7. As the cassette 3.sub.1 or 3.sub.2 is further pushed
against the resistance due to such abutment, the locking arm 7 is rotated
around the support shaft 5 in an anti-clockwise direction against the
action of the spring 6 by the inclined cam surface 3b to ride on the upper
surface of the guide ridge 3a. Subsequently, as shown in FIG. 2B, the
downwardly extending projection 7a of the locking arm is engaged by a
locking recess 3c formed in the upper surface of the guide ridge 3a of the
cassette. In this point, the cassette has reach a predetermined mounted
position where the cassette is stably held in the mounted condition
through the engagement between the projection 7a and the locking recess
3c.
On the other hand, if the mounted cassette 3.sub.1 or 3.sub.2 is dismounted
from the cassette insertion portion 2, the cassette is pulled or withdrawn
in a cassette removal direction with a force stronger than a cassette
holding force due to the engagement between the projection 7a and the
locking recess 3c. As a result, the locking arm is rotated in an
anti-clockwise direction against the action of the spring 6 to disengage
the projection 7a of the locking arm from the locking recess 3c of the
cassette, thus releasing the cassette from the locking means.
Subsequently, the cassette can be easily pulled out of the cassette
insertion portion without any resistance.
In the mounted condition where the two cassettes 3.sub.1, 3.sub.2 are
received in the cassette insertion portion 2 in the overlapped relation as
shown in FIGS. 1B and 1C, the kinds of the sheets accommodated in the two
mounted cassettes are detected by detection means (not shown),
respectively, and the detected kinds of the sheets are displayed on a
displayer of the selection designation means arranged on a console panel
(not shown) of the body 1 of the apparatus.
When the operator selects or designates the desired kinds of sheet from
among the display kinds of sheet, only the sheet feeding means 2.sub.1 or
2.sub.2 corresponding to the cassette 3.sub.1 or 3.sub.2 including the
designated sheets can be actuated. In this way, such sheet feeding means
2.sub.1 or 2.sub.2 is controlled to be actuated to feed the designated
sheets one by one toward a predetermined sheet processing position in the
body 1 of the apparatus through a sheet path 22.sub.1 or 22.sub.2, regist
rollers 23 and sheet passage 24.
FIG. 3 is an explanatory view showing an example that the present invention
is incorporated into a body of the apparatus 40 (a printer as an image
forming apparatus).
As shown in FIG. 3, the printer 40 includes an image forming portion 45
comprising a photosensitive drum 43 arranged within a frame 42 of the
printer at a substantially central position thereof, and a sheet ejector
tray 46 arranged on a left side (FIG. 3) of the printer frame. In the
image forming portion 45, a primary charger 47, developing device 49
including developer such as toner therein, transfer charger 50, separation
charger 51 and cleaner 52 are arranged around the photosensitive drum 43.
Further, a feeding belt 53, fixing device 55 and ejector rollers 56 are
arranged between the image forming portion 45 and the sheet ejector tray
46.
When a sheet feeding signal is emitted, the sheet P accommodated in the
cassette 3.sub.1 or 3.sub.2 is fed toward the image forming portion 45 of
the printer 40 by means of the sheet feeding means 2.sub.1 or 2.sub.2
until a leading edge of the sheet P abuts against the regist rollers 23.
Then, when the regist rollers 23 are actuated to initiate the conveying of
the sheet P, the sheet P is skew-fed to be directed between the
photosensitive drum 43 and the transfer charger 50 while being pinched by
the regist rollers 23. On the other hand, the regist rollers 23 are
stopped when a trailing edge of the sheet P leaves therefrom.
A toner image formed by an electrophotographic process is transferred from
the photosensitive drum 43 onto the sheet P fed between the photosensitive
drum 43 and the transfer charger 50, and then, the sheet P is separated
from the photosensitive drum 43 by separation means such as the separation
charger 51 and the like and then is conveyed by the feeding belt 53 to the
fixing device 55 where the transferred image is fixed. Then, the sheet P
is ejected or discharged into the ejector tray 56.
FIGS. 1D and 1E show a condition that a cassette 3.sub.3 having a larger
capacity is mounted in the cassette insertion portion 2. In this case, the
cassette 3.sub.3 has a sheet accommodating capacity larger than that of
the cassette 3.sub.1 or 3.sub.2 by about twice. Similarly to the cassettes
3.sub.1, 3.sub.2, the cassette 3.sub.3 is also provided at its both upper
side walls with guide ridges 3a which can engage by the upper guide slots
2a of the cassette insertion portion 2.
After the both of the cassettes 3.sub.1 and 3.sub.2 each having the smaller
capacity are removed from the cassette insertion portion 2, the cassette
3.sub.3 having the larger capacity is mounted in the cassette insertion
portion 2 by inserting it completely into the cassette insertion portion 2
while engaging the guide ridges 3a thereof by the corresponding upper
guide slots 2a until the cassette 3.sub.3 is locked and positioned by the
above-mentioned locking means 7, 3c (FIG. 2). In this case, the cassette
3.sub.3 having the larger capacity is mounted across the feeding means
2.sub.1, 2.sub.2 in association with only the upper feeding means 2.sub.1.
In this case, only the upper feeding means 2.sub.1 is actuated to
automatically feed the sheets one by one from the cassette 3.sub.3 of the
larger capacity.
Incidentally, as shown in FIG. 1B, each of the cassettes 3.sub.1, 3.sub.2
having the smaller capacity and the cassette 3.sub.3 having the larger
capacity is provided with a rockable plate 3c' on which the sheets P are
stacked. Each rockable plate 3c' is always biased in an upper direction so
that the leading edge portion of the uppermost sheet P on the stack is
lifted to contact with the associated feeding means 2.sub.1, 2.sub.2.
Further, sheet separating pawls (not shown) are provided in the cassette
to engage with the leading edge portion or side edges of the uppermost
sheet. Since such construction of the cassette is already known, the
detailed explanation thereof will be omitted.
FIG. 4 shows a second embodiment of the present invention.
In this second embodiment, three (upper, intermediate, lower) sheet feeding
means 2.sub.1, 2.sub.2 and 2.sub.3 are provided in association with a
single cassette insertion portion 2, and, as shown in FIGS. 4B and 4C,
three sheet cassettes 3.sub.1, 3.sub.2 and 3.sub.3 each having a smaller
capacity can be inserted into the single cassette insertion portion 2 in
an overlapped relation to feed the sheet from the sheet cassette 3.sub.1,
3.sub.2 or 3.sub.3 selectively.
Alternatively, as shown in FIGS. 4D and 4E, after the intermediate and
lower cassettes 3.sub.2 and 3.sub.3 of the smaller capacity are removed
from the cassette insertion portion 2, when a sheet cassette 3.sub.4
having an middle sheet accommodating capacity larger than that of the
cassette 3.sub.2, 3.sub.3 by about twice is inserted into space obtained
by the removal of the cassettes 3.sub.2, 3.sub.3, the sheet can be
selectively fed from the middle cassette 3.sub.4 or from the smaller
cassette 3.sub.1.
Further, as shown in FIGS. 4F and 4G, after all of the smaller cassettes
3.sub.1, 3.sub.2 and 3.sub.3 are removed from the cassette insertion
portion 2, when a sheet cassette 3.sub.5 having a larger sheet
accommodating capacity larger than that of the smaller cassette by about
three times is inserted into the cassette insertion portion 2 in place of
these smaller cassettes, the sheets in the larger cassette 3.sub.5 can
exclusively be used.
The middle cassette 3.sub.4 shown in FIGS. 4D and 4E is positioned in the
locked position by means of the locking means provided in association with
the intermediate guide slots 2b of the cassette insertion portion 2.
Similarly, the larger cassette 3.sub.5 shown in FIGS. 4D and 4E is
positioned in the locked position by means of the locking means provided
in association with the upper guide slots 2b of the cassette insertion
portion 2.
FIG. 5 shows a third embodiment of the present invention.
In this third embodiment, the cassette insertion portion is divided into
three (upper, intermediated, lower) cassette insertion portions 26.sub.1,
26.sub.2 and 26.sub.3 with which the sheet feeding means 2.sub.1, 2.sub.2
and 2.sub.3 are associated, respectively. More particularly, these
cassette insertion portions are separated from each other in an
up-and-down direction by means partition plates 27.sub.1 and 27.sub.2
which are removably mounted in the cassette insertion portion and on which
the sheet cassettes are supported, respectively. The partition plates
27.sub.1, 27.sub.2 are normally inserted into and supported by guide
recesses 28a formed in both side walls of the cassette insertion portion,
and are prevented from slipping out of the cassette insertion portion by
means of pins or other appropriate fastening means (not shown), thus
dividing the cassette insertion portion into three-layer (upper,
intermediate, lower) cassette insertion portions 26.sub.1, 26.sub.2 and
26.sub.3.
As shown in FIG. 5C, when the sheet cassettes 3.sub.1, 3.sub.2 and 3.sub.3
each having a smaller capacity are mounted in the corresponding cassette
insertion portions 26.sub.1, 26.sub.2 and 26.sub.3, the sheet can be fed
from the sheet cassette 3.sub.1, 3.sub.2 or 3.sub.3 selectively.
Alternatively, after the upper partition plate 27.sub.1 is removed to
continue or combine the upper and intermediate cassette insertion portions
26.sub.1, 26.sub.2, when the cassette 3.sub.4 having the middle capacity
is inserted in the combined cassette insertion portion, the sheet can be
fed from the middle cassette 3.sub.4 or from the smaller cassette 3.sub.3
selectively. Similarly, the lower partition plate 27.sub.2 may be removed
to continue or combine the intermediate and lower cassette insertion
portions 26.sub.2, 26.sub.3 into which the middle cassette 3.sub.4 can be
inserted.
Further, as shown in FIG. 5E, after both of the upper and lower partition
plates 27.sub.1, 27.sub.2 are removed to combine all of the cassette
insertion portions 26.sub.1, 26.sub.2 and 26.sub.3, when the larger
cassette 3.sub.5 is inserted into the combined cassette insertion portion,
the sheets can be fed from the larger cassette exclusively.
FIG. 6 shows a fourth embodiment of the present invention.
While, in the above first, second and third embodiments, the sheet feeding
means 2.sub.1 -2.sub.3 associated with the respective cassette insertion
portions were arranged in a staggered relation as shown in FIGS. 6A-6C,
these feeding means 2.sub.1 -2.sub.3 can be arranged on a substantially
vertical line, by changing an angle of the mounting of each cassette
3.sub.1 -3.sub.5 with respect to the cassette insertion portion 2.
Further, the arrangement of the sheet feeding means may be optionally
altered by changing the angle of the mounting of each cassette with
respect to the cassette insertion portion.
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